The present invention relates to a vehicle seat, in particular an automobile seat, with a height adjuster for adjusting the height of a seat frame of the vehicle seat relative to the vehicle structure.
In known vehicle seats of the above described kind, forces occurring in the event of a crash are transmitted from the seat frame, via the height adjuster, to the vehicle structure. In particular in the case of height adjusters that are actuatable by a motor, this disadvantageously stresses their drive, which is normally located between the seat frame and a movable element of the height adjuster.
In accordance with one aspect of the present invention, a vehicle seat is provided that performs advantageously in the event of a crash. In accordance with this aspect, the vehicle seat includes a seat frame mounted to a height adjuster. The height adjuster is for being connected between the seat frame and a vehicle structure, and adjusting the height of the seat frame relative to the vehicle structure. Further according to this aspect, a locking device is mounted to the vehicle seat for securing the height adjuster in a normal position during a normal condition, and for releasing the height adjuster in response to a crash in which the vehicle seat experiences at least a predetermined load. The locking device is provided with at least one stop that is engaged in response to the releasing of the locking device to establish an alternative force transmission path between the seat frame and the vehicle structure.
As a result of providing a locking device with a stop, which makes available an alternative force transmission between the seat frame and the vehicle structure in the event of a crash, it is possible to transmit the crash forces from the seat frame, for example, directly into the seat rails and, thus, into the vehicle floor as a part of the vehicle structure. This relieves a drive for the height adjuster, which is operative between the seat frame and the height adjuster, and protects the drive against destruction. The term xe2x80x9cseat framexe2x80x9d is understood to include other kinds of seat cushion supports and seat back supports. Because the locking device is designed to transmit a force in the event of a crash, the stop differs from simple, supplementary locking devices, which solely function to prevent an opening of the respective main locking devices.
Preferably, the locking device is designed and constructed such that the stop responds irrespective of the adjusted height of the vehicle seat, namely each time about equally fast. It is preferred to provide two stops, which are operative in two different load directions and, thus, are in some ways not dependent on the type of load, i.e., they are operative both in a front end crash and in a rear end crash, but remain deactivated in the case of working loads and abusive loads. Preferably, activation occurs when a limit load is exceeded, in that, for example, the respective stop engages.
Preferably, the stop is activated by a change in geometry within the height adjuster. If the height adjuster is designed and constructed as a coupler mechanism, a preferably elastic and therefore reversible deformation of the height adjuster will be able to occur within a four-bar linkage, on the hump side or door sill side, or between the two four-bar linkages. Examples for reversible stop activations are spring elements or a force limit locking device with a reset element. The force needed for deforming the height adjuster corresponds to the aforesaid limit force.
In a preferred embodiment with a limit force locking device for activating the stop, a movably supported, spring-loaded locking pawl secures a bearing pin of a rocking arm of the height adjuster in the normal condition of the locking device. In the event of a crash, upon exceeding the limit force, the stop pawl releases the bearing pin for displacement in a guideway. This causes the geometry of the height adjuster to change, which then activates the stop. The spring force, which embodies the response threshold of the limit force locking device, and the arrangement of the guideway depend on the realization of the height adjuster kinematics and the occurring crash loads. It is necessary that the limit force locking device be capable of clearly disengaging and the stop of engaging over the entire height adjustment range and for each case of crash (front end crash and rear end crash).
In a further preferred embodiment, the load transmitting stop is located between the height adjuster and the seat frame. In this instance, at least one movably supported toothed pawl is located either on the height adjuster or on the seat frame, and an associated toothed element is provided respectively on the other part, with the toothed pawl and toothed element engaging each other in the event of a crash. It is preferred to provide for the front end crash and the rear end crash respectively one toothed pawl and respectively one associated toothed element. Preferably, the two thus-formed gear tooth systems do not mutually exert on each other any expelling forces in the event of a crash. The subdivision into two separate, load-direction-dependent stops has the advantage that it is possible to realize by nesting a load-level-adapted dimensioning and an axial securement of the stops being engaged.
In a particularly preferred embodiment, the limit force locking device for the activation and the stops for the load transmission are parts of a common locking device, for example, in that the locking pawl and the toothed pawls are provided on a common, movably supported lever. This simplifies manufacture of the locking device and makes it more cost favorable.